Communication system

ABSTRACT

A communication system is described in which an MBMS service is provided by unicast or broadcast/multicast communication in dependence on whether the number of mobile communication devices indicating an interest in receiving the service is below or above a broadcast threshold. An improved procedure for counting the number of mobile communication devices interested in receiving the MBMS service is also disclosed.

TECHNICAL FIELD

The present invention relates to a communication system, and tocomponents thereof, for the provision of services to mobile devices, andin particular to a communication system and components for the provisionof multimedia services. The invention has particular, though notexclusive, relevance to the provision of a Multimedia BroadcastMulticast Service (MBMS) via Long Term Evolution (LTE) radio technologyas defined in the 3rd Generation Partnership Project (3GPP) standardsdocumentation including, for example, the most recent versions of: TS36.300 V9.5.0 (‘E-UTRA and E-UTRAN; Overall description; Stage 2’); TS36.331 V8.11.0 (‘E-UTRAN; Radio Resource Control protocol’); TS 36.443V9.2.0 (‘E-UTRAN; M2 Application Protocol (M2AP)’); TS 36.444 V9.2.0(‘E-UTRAN; M3 Application Protocol (M3AP)’); and TS 23.246 V9.5.0(‘MBMS; Architecture and functional description’).

BACKGROUND ART

Currently, as its name implies, MBMS transmission in LTE makes use of abroadcast mode to provide multimedia services and associated content tothe user equipment (UE) such as mobile telephones/‘cell’ phones or othersuch communication devices. The broadcast of the multimedia services isachieved using LTE's MBMS Single Frequency Network (MBSFN) transmissionin which multiple LTE Base Stations (so called ‘evolved NodeBs’ or‘eNBs’) combine the MBMS data transmission on multiple cells. In view ofthe complexity of the broadcast mechanism, it is only used by thenetwork if there are a sufficient number of interested users, for agiven MBMS service, to warrant provision of the service using thebroadcast transmission mode. Accordingly, in this scenario, if aninsufficient number of users have expressed an interest in a particularmultimedia service, the multimedia service will not be provided.

Furthermore, the mechanisms previously considered for determining thenumber of users in a particular coverage area who wish to receive aparticular service are inaccurate, tending to undercount the number ofactual interested users. In part this is because the network is unableto derive the necessary information, from many of the devices in thecoverage area, to determine if their respective users wish to receivethe service or not. Thus, even when there are a sufficient number ofinterested users in a coverage area to warrant provision of themultimedia service using the broadcast transmission mode the multimediaservice may, nevertheless, still be withheld.

SUMMARY

The invention therefore aims to provide a communication system andcomponents thereof, which addresses or at least alleviates the aboveissues.

One proposal considered by the inventors, for helping to ensure thatusers who are interested in receiving a particular multimedia serviceare provided with that service, regardless the number of interestedusers, is to allow the provision of multimedia service using unicastcommunication under certain conditions. Specifically, delivery viaunicast communication is provided when the number of interested users isbelow a particular threshold (e.g. a threshold below which the provisionof the multimedia service using the broadcast transmission mode isunwarranted) and delivery via multicast or broadcast communication isprovided when the number of interested users is above that threshold.

The implementation of such a proposal is, however, not trivial, in partbecause there are currently no mechanisms that would allow the provisionof unicast transmission to mobile communication devices, for an MBMSservice for which the number of interested users is under a thresholdbelow which multicast transmission is deemed not be worthwhile.

In one embodiment, the invention provides a method performed in acommunication system (by respective components thereof) comprising:determining the number of mobile communications devices, in a coveragearea for an MBMS service, that have indicated an interest in receivingthat MBMS service; comparing the result of the determination with apre-determined threshold (e.g. a threshold above which broadcast and/ormulticast communication is deemed to be acceptable); and providing theMBMS service by unicast or broadcast/multicast in dependence on thecomparison.

For example, if the comparison finds the result of the determination tobe less than (or at least not greater than) the threshold, the MBMSservice may be provided by unicast. If the comparison finds the resultof the determination to be greater than (or at least not less than thethreshold), then the MBMS service may be provided by broadcast ormulticast.

To facilitate the provision of unicast communication, the inventors havealso formulated significant improvements in the way that the networkdetermines the number of interested users. Specifically, the inventorshave developed a method which allows the network not only to count thedevices which are active (or have had an active connection at anappropriate time) but also to count devices which are camped in thecoverage area but are inactive.

According to one aspect of the invention there is provided a mobilecommunication device for a communication system, which communicationsystem is operable to deliver Mobility Broadcast/Multicast Service(MBMS) services, the mobile communication device comprising: means forregistering the mobile communication device with a base station; meansfor operating in an idle mode in which the mobile communication deviceis registered with the base station but does not have an activeconnection to the base station; means for determining the identity of anMBMS service that is to be made available; and means for indicating aninterest in receiving said MBMS service to said base station when saiddetermining means has determined that said MBMS is to be made available;wherein said indicating means is operable, when said mobilecommunication device is in said idle mode, to indicate said interest by:initiating communications, with said base station, to establish anactive connection; sending at least one message to said base station,during or after establishment of said active connection, to indicatethat said establishment of an active connection is for the purposes ofindicating an interest in an MBMS service.

According to another aspect of the invention there is provided a basestation for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the base station comprising: means for registering a pluralityof mobile communication devices with the base station wherein at leastone of said mobile communication device is operating in an idle mode inwhich the mobile communication device is registered but does not have anactive connection to the base station; means for receiving an indicationthat a procedure should be initiated for counting the number of mobilecommunication devices that indicate an interest in receiving a specifiedMBMS service and that are registered with the base station; and meansfor indicating, to said plurality of mobile communication devices, theidentity the specified MBMS service; means for identifying an indicationof interest in the specified MBMS service from any of said plurality ofmobile communication devices; wherein said identifying means is operableto identify an indication of interest in the specified MBMS service,from the at least one mobile communication device operating in an idlemode, by: entering communications, with the at least one mobilecommunication device operating in an idle mode, to establish an activeconnection; receiving at least one message from the at least one mobilecommunication device operating in an idle mode, during or afterestablishment of said active connection, to indicate that saidestablishment of an active connection is for the purposes of indicatingan interest in said MBMS service; determining that said establishment ofan active connection is for the purposes of indicating an interest insaid MBMS service; and identifying the MBMS service to which said atleast one message relates; means for compiling information foridentifying a number of mobile communication devices that have indicatedan interest in the MBMS service; and means for providing, to a networkentity, the compiled information for identifying the number of mobilecommunication devices that have indicated an interest in the MBMSservice.

According to another aspect of the invention there is provided a networkentity for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the network entity comprising: means for receiving a requestto start an MBMS session for a specified MBMS service from a furthernetwork entity; means for determining that a procedure should beinitiated for counting the number of mobile communication devices thatindicate an interest in receiving said specified MBMS service; means forindicating, to at least one base station, that said procedure should beinitiated for counting the number of mobile communication devices thatindicate an interest in receiving said specified MBMS service and thatare registered with said at least one base station; means for receiving,from said at least one base station, information for identifying anumber of mobile communication devices that have indicated an interestin the MBMS service, wherein said number of mobile communication devicesthat have indicated an interest in the MBMS service includes at leastone mobile communication device that was operating in an idle mode whensaid counting procedure was initiated; means for comparing said numberof mobile communication devices that have indicated an interest in theMBMS service with a predetermined threshold; means for generating, whensaid comparison indicates that said number of mobile communicationdevices that have indicated an interest in the MBMS service is belowsaid predetermined threshold, a response to said request to start anMBMS session, wherein said response includes an indication thatinitiation of said number of mobile communication devices that haveindicated an interest in the MBMS service is below said predeterminedthreshold; and means for sending said generated response to said furthernetwork entity.

According to another aspect of the invention there is provided a networkentity for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the network entity comprising: means for determining that aprocedure should be initiated for counting the number of mobilecommunication devices that indicate an interest in receiving a specifiedMBMS service that is currently being delivered via broadcast/multicast;means for indicating, to at least one base station, that said procedureshould be initiated for counting the number of mobile communicationdevices that indicate an interest in receiving said specified MBMSservice and that are registered with said at least one base station;means for receiving, from said at least one base station, informationfor identifying a number of mobile communication devices that haveindicated an interest in the MBMS service, wherein said number of mobilecommunication devices that have indicated an interest in the MBMSservice includes at least one mobile communication device that wasoperating in an idle mode when said counting procedure was initiated;means for comparing said number of mobile communication devices thathave indicated an interest in the MBMS service with a predeterminedthreshold; means for generating, when said comparison indicates thatsaid number of mobile communication devices that have indicated aninterest in the MBMS service is below said predetermined threshold, amessage to stop said specified MBMS service, wherein said responseincludes an indication that said number of mobile communication devicesthat have indicated an interest in the MBMS service is below saidpredetermined threshold; and means for sending said generated message toa further network entity.

According to another aspect of the invention there is provided a networkentity for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the network entity comprising: means for sending, to a secondnetwork entity, a request to start an MBMS session for a specified MBMSservice; means for receiving, from said second network entity, aresponse to said request to start an MBMS session, wherein said responseincludes an indication that a number of mobile communication devicesthat have indicated an interest in the MBMS service is below apredetermined threshold; and means for determining that said MBMSservice is to be delivered by unicast communication in response to saidindication that a number of mobile communication devices that haveindicated an interest in the MBMS service is below a predeterminedthreshold.

According to another aspect of the invention there is provided networkentity for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the network entity comprising: means for sending, to a secondnetwork entity, a request to start an MBMS session for a specified MBMSservice; means for receiving, from said second network entity, a messageto stop a specified MBMS service that is currently being delivered bybroadcast/multicast, wherein said message includes an indication thatsaid number of mobile communication devices that have indicated aninterest in the MBMS service is below said predetermined threshold; andmeans for determining that said MBMS service is to be delivered byunicast communication in response to said indication that a number ofmobile communication devices that have indicated an interest in the MBMSservice is below a predetermined threshold.

According to another aspect of the invention there is provided a basestation for a communication system, which communication system isoperable to deliver Mobility Broadcast/Multicast Service (MBMS)services, the base station comprising: means for receiving, from anetwork entity, a request to set up a radio bearer for the delivery ofan MBMS service via unicast to a mobile communication device; means forgenerating, in response to receipt of said request to set up a radiobearer, a message (e.g. an RRC message such as an RRC ConnectionReconfiguration message) to configure said radio bearer, at said mobilecommunication device, for the delivery of the MBMS service via unicast;means for sending, to said mobile communication device, said generatedmessage to configure said radio bearer for the delivery of the MBMSservice via unicast; means for receiving, from said mobile communicationdevice, a message indicating (e.g. an RRC message such as an RRCConnection Reconfiguration Complete message) that said radio bearer hasbeen configured by said mobile communication device for receipt of theMBMS service via unicast; means for generating, in response to receiptof said message indicating that said radio bearer has been configured bysaid mobile communication device for receipt of the MBMS service viaunicast, a response to said request to set up a radio bearer for thedelivery of the MBMS service via unicast; and means for sending saidgenerated response to said network entity.

According to another aspect of the invention there is provided a mobilecommunication device for a communication system, which communicationsystem is operable to deliver Mobility Broadcast/Multicast Service(MBMS) services, the mobile communication device comprising: means forreceiving, from a base station, a message to configure a radio bearerfor the delivery of the MBMS service via unicast; means for configuringsaid radio bearer for receipt of said MBMS service via unicast inresponse to receipt of said message to configure said radio bearer;means for generating, a message indicating that said radio bearer hasbeen configured by said mobile communication device for receipt of theMBMS service via unicast; and means for sending said generated messageto said base station.

According to another aspect of the invention there is provided a mobilecommunication device for a communication system, which communicationsystem is operable to deliver Mobility Broadcast/Multicast Service(MBMS) services, the mobile communication device comprising: means fordetermining an identity of an MBMS service that said mobilecommunication device is to be made available; means for indicating aninterest in said MBMS service to a network entity; means for determiningthat an identifier of said MBMS service in which said interest has beenindicated is absent from a control channel; and means for initiating, inresponse to the absence of said identifier, delivery of said MBMSservice in which said interest has been indicated via unicastcommunication.

According to another aspect of the invention there is provided a mobilecommunication device for a communication system, which communicationsystem is operable to deliver Mobility Broadcast/Multicast Service(MBMS) services, the mobile communication device comprising: means fordetermining an identity of an MBMS service that is to be made available;means for indicating an interest in said MBMS service to a networkentity; means for determining that an identifier of said MBMS service inwhich said interest has been indicated is absent from a control channel;and means for initiating, in response to the absence of said identifier,delivery of said MBMS service in which said interest has been indicatedvia unicast communication.

According to another aspect of the invention there is provided a methodperformed by a mobile communication device of a communication system,which communication system is operable to deliver MobilityBroadcast/Multicast Service (MBMS) services, the method comprising:registering the mobile communication device with a base station;operating in an idle mode in which the mobile communication device isregistered with the base station but does not have an active connectionto the base station; determining the identity of an MBMS service that isto be made available; and indicating an interest in receiving said MBMSservice to said base station when said determining means has determinedthat said MBMS is to be made available; wherein said indicating stepcomprises, when said mobile communication device is in said idle mode,indicating said interest by: initiating communications, with said basestation, to establish an active connection; sending at least one messageto said base station, during or after establishment of said activeconnection, to indicate that said establishment of an active connectionis for the purposes of indicating an interest in an MBMS service.

According to another aspect of the invention there is provided a methodperformed by a base station of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the method comprising: registering a pluralityof mobile communication devices with the base station wherein at leastone of said mobile communication device is operating in an idle mode inwhich the mobile communication device is registered but does not have anactive connection to the base station; receiving an indication that aprocedure should be initiated for counting the number of mobilecommunication devices that indicate an interest in receiving a specifiedMBMS service and that are registered with the base station; andindicating, to said plurality of mobile communication devices, theidentity the specified MBMS service; identifying an indication ofinterest in the specified MBMS service from any of said plurality ofmobile communication devices; wherein said identifying step comprisesidentifying an indication of interest in the specified MBMS service,from the at least one mobile communication device operating in an idlemode, by: entering communications, with the at least one mobilecommunication device operating in an idle mode, to establish an activeconnection; receiving at least one message from the at least one mobilecommunication device operating in an idle mode, during or afterestablishment of said active connection, to indicate that saidestablishment of an active connection is for the purposes of indicatingan interest in said MBMS service; determining that said establishment ofan active connection is for the purposes of indicating an interest insaid MBMS service; and identifying the MBMS service to which said atleast one message relates; compiling information for identifying anumber of mobile communication devices that have indicated an interestin the MBMS service; and providing, to a network entity, the compiledinformation for identifying the number of mobile communication devicesthat have indicated an interest in the MBMS service.

According to another aspect of the invention there is provided a methodperformed by a network entity of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the method comprising: receiving a request tostart an MBMS session for a specified MBMS service from a furthernetwork entity; determining that a procedure should be initiated forcounting the number of mobile communication devices that indicate aninterest in receiving said specified MBMS service; indicating, to atleast one base station, that said procedure should be initiated forcounting the number of mobile communication devices that indicate aninterest in receiving said specified MBMS service and that areregistered with said at least one base station; receiving, from said atleast one base station, information for identifying a number of mobilecommunication devices that have indicated an interest in the MBMSservice, wherein said number of mobile communication devices that haveindicated an interest in the MBMS service includes at least one mobilecommunication device that was operating in an idle mode when saidcounting procedure was initiated; comparing said number of mobilecommunication devices that have indicated an interest in the MBMSservice with a predetermined threshold; generating, when said comparisonindicates that said number of mobile communication devices that haveindicated an interest in the MBMS service is below said predeterminedthreshold, a response to said request to start an MBMS session, whereinsaid response includes an indication that initiation of said number ofmobile communication devices that have indicated an interest in the MBMSservice is below said predetermined threshold; and sending saidgenerated response to said further network entity.

According to another aspect of the invention there is provided a methodperformed by a network entity of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the method comprising: determining that aprocedure should be initiated for counting the number of mobilecommunication devices that indicate an interest in receiving a specifiedMBMS service that is currently being delivered via broadcast/multicast;indicating, to at least one base station, that said procedure should beinitiated for counting the number of mobile communication devices thatindicate an interest in receiving said specified MBMS service and thatare registered with said at least one base station; receiving, from saidat least one base station, information for identifying a number ofmobile communication devices that have indicated an interest in the MBMSservice, wherein said number of mobile communication devices that haveindicated an interest in the MBMS service includes at least one mobilecommunication device that was operating in an idle mode when saidcounting procedure was initiated; comparing said number of mobilecommunication devices that have indicated an interest in the MBMSservice with a predetermined threshold; generating, when said comparisonindicates that said number of mobile communication devices that haveindicated an interest in the MBMS service is below said predeterminedthreshold, an indication to stop said specified MBMS session, whereinsaid indication includes an indication that initiation of said number ofmobile communication devices that have indicated an interest in the MBMSservice is below said predetermined threshold; and sending saidgenerated response to a further network entity.

According to another aspect of the invention there is provided a methodperformed by a network entity of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the method comprising: sending, to a secondnetwork entity, a request to start an MBMS session for a specified MBMSservice; receiving, from said second network entity, a response to saidrequest to start an MBMS session, wherein said response includes anindication that a number of mobile communication devices that haveindicated an interest in the MBMS service is below a predeterminedthreshold; and determining that said MBMS service is to be delivered byunicast communication in response to said indication that a number ofmobile communication devices that have indicated an interest in the MBMSservice is below a predetermined threshold.

According to another aspect of the invention there is provided a methodperformed by a network entity of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the network entity comprising: sending, to asecond network entity, a request to start an MBMS session for aspecified MBMS service; receiving, from said second network entity, anindication to stop a specified MBMS service that is currently beingdelivered by broadcast/multicast, wherein said indication includes anindication that said number of mobile communication devices that haveindicated an interest in the MBMS service is below said predeterminedthreshold; and determining that said MBMS service is to be delivered byunicast communication in response to said indication that a number ofmobile communication devices that have indicated an interest in the MBMSservice is below a predetermined threshold.

According to another aspect of the invention there is provided a methodperformed by a base station of a communication system, whichcommunication system is operable to deliver Mobility Broadcast/MulticastService (MBMS) services, the method comprising: receiving, from anetwork entity, a request to set up a radio bearer for the delivery ofan MBMS service via unicast to a mobile communication device;generating, in response to receipt of said request to set up a radiobearer, a message (e.g. an RRC message such as an RRC ConnectionReconfiguration message) to configure said radio bearer, at said mobilecommunication device, for the delivery of the MBMS service via unicast;sending, to said mobile communication device, said generated message toconfigure said radio bearer for the delivery of the MBMS service viaunicast; receiving, from said mobile communication device, a messageindicating (e.g. an RRC message such as an RRC ConnectionReconfiguration Complete message) that said radio bearer has beenconfigured by said mobile communication device for receipt of the MBMSservice via unicast; generating, in response to receipt of said messageindicating that said radio bearer has been configured by said mobilecommunication device for receipt of the MBMS service via unicast, aresponse to said request to set up a radio bearer for the delivery ofthe MBMS service via unicast; and means for sending said generatedresponse to said network entity.

According to another aspect of the invention there is provided a methodperformed by a mobile communication device of a communication system,which communication system is operable to deliver MobilityBroadcast/Multicast Service (MBMS) services, the method comprising:receiving, from a base station, a message to configure a radio bearerfor the delivery of the MBMS service via unicast; configuring said radiobearer for receipt of said MBMS service via unicast in response toreceipt of said message to configure said radio bearer; generating, amessage indicating that said radio bearer has been configured by saidmobile communication device for receipt of the MBMS service via unicast;and sending said generated message to said base station.

According to another aspect of the invention there is provided a methodperformed by a mobile communication device of a communication system,which communication system is operable to deliver MobilityBroadcast/Multicast Service (MBMS) services, the method comprising:determining an identity of an MBMS service that said mobilecommunication device is to be made available; indicating an interest insaid MBMS service to a network entity; determining that an identifier ofsaid MBMS service in which said interest has been indicated is absentfrom a control channel; and initiating, in response to the absence ofsaid identifier, delivery of said MBMS service in which said interesthas been indicated via unicast communication.

According to another aspect of the invention there is provided a methodperformed by a mobile communication device of a communication system,which communication system is operable to deliver MobilityBroadcast/Multicast Service (MBMS) services, the method comprising:determining an identity of an MBMS service that is to be made available;indicating an interest in said MBMS service to a network entity;determining that an identifier of said MBMS service in which saidinterest has been indicated is absent from a control channel; andinitiating, in response to the absence of said identifier, delivery ofsaid MBMS service in which said interest has been indicated via unicastcommunication.

Aspects of the invention extend to computer program products such ascomputer readable storage media having instructions stored thereon whichare operable to program a programmable processor to carry out a methodas described in the aspects and possibilities set out above or recitedin the claims and/or to program a suitably adapted computer to providethe apparatus recited in any of the claims.

Each feature disclosed in this specification (which term includes theclaims) and/or shown in the drawings may be incorporated in theinvention independently (or in combination with) any other disclosedand/or illustrated features. In particular but without limitation thefeatures of any of the claims dependent from a particular independentclaim may be introduced into that independent claim in any combinationor individually.

The description of the invention with reference to the drawings is byway of example only.

The text of the abstract filed herewith is repeated here as part of thespecification. In an exemplary aspect of the invention of the inventionthere is provided a communication system is described in which an MBMSservice is provided by unicast or broadcast/multicast communication independence on whether the number of mobile communication devicesindicating an interest in receiving the service is below or above abroadcast threshold. An improved procedure for counting the number ofmobile communication devices interested in receiving the MBMS service isalso disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of exampleonly with reference to the attached figures in which:

FIG. 1 shows, in simplified overview, a schematic of an architecture forthe provision of multimedia broadcast/multicast services (MBMS) in acommunication system;

FIG. 2 shows, in simplified overview, a schematic of an architecture forthe provision of unicast communication in the communication system ofFIG. 1;

FIG. 3 is a simplified block diagram of a mobile communication deviceforming part of the system shown in FIGS. 1 and 2;

FIG. 4 is a simplified block diagram of a base station forming part ofthe system shown in FIGS. 1 and 2;

FIG. 5 is a simplified block diagram of a Multi-cell/MulticastCoordination Entity (MCE) forming part of the system shown in FIG. 1;

FIG. 6 is a simplified block diagram of a mobility management entity(MME) forming part of the system shown in FIGS. 1 and 2;

FIG. 7 is a simplified block diagram of an MBMS Gateway (MBMS-GW)forming part of the system shown in FIG. 1;

FIG. 8 is a simplified block diagram of a Broadcast-Multicast ServiceCentre (BM-SC) forming part of the system shown in FIG. 1;

FIG. 9 is a simplified block diagram of a combined ServingGateway/Packet Data Network Gateway (SGW/PDN-GW) forming part of thesystem shown in FIG. 2;

FIG. 10 is a high level flow chart illustrating a procedure implementedby the communication system 1 to selectively provide an MBMS service byunicast and/or by broadcast/multicast;

FIG. 11 is a simplified timing diagram illustrating an MBMS sessionservice start phase of the procedure of the procedure of FIG. 10;

FIG. 12 is a simplified timing diagram illustrating an idle mode part ofa counting phase of the procedure of FIG. 10;

FIG. 13 is a simplified timing diagram illustrating an active mode partof a counting phase of the procedure of FIG. 10;

FIG. 14 is a simplified timing diagram illustrating a thresholdcomparison phase of the procedure of FIG. 10;

FIG. 15 is a simplified timing diagram illustrating an initial part of aunicast activation phase of the procedure of FIG. 10;

FIG. 16 is a simplified timing diagram illustrating a further part ofthe unicast activation phase of the procedure of FIG. 10;

FIG. 17 is a simplified timing diagram illustrating an MBMS service viabroadcast/multicast activation phase of the procedure of FIG. 10;

FIG. 18 is a simplified timing diagram illustrating an MBMS service viabroadcast/multicast deactivation phase of the procedure of FIG. 10;

FIG. 19 is a simplified timing diagram illustrating a possible variationof the idle mode part of the counting phase of the procedure of FIG. 10;

FIG. 20 is a simplified timing diagram illustrating a further possiblevariation of the idle mode part of the counting phase of the procedureof FIG. 10;

FIG. 21 is a simplified timing diagram illustrating a possible variationof the further part of the unicast activation phase of the procedure ofFIG. 10;

FIG. 22 is a simplified timing diagram illustrating a possible variationof a unicast activation phase of the procedure of FIG. 10; and

FIG. 23 is a simplified timing diagram illustrating a possible variationof a broadcast/multicast phase of the procedure of FIG. 10.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Overview

FIGS. 1 and 2 each schematically illustrates a mobile (cellular)communication system 1 for providing MBMS services. The communicationsystem 1 comprises user equipment 3, including a plurality of mobilecommunication devices 3-1, 3-2 (also referred to herein as UEs) servedby a base station 5. In this embodiment, the base station 5 is an LTEbase station (also referred to herein as an ‘evolved NodeB’ or ‘eNB’)forming part an Evolved Universal Technology Radio Access Network(E-UTRAN). The telecommunication system 1 also comprises core network 8comprising and Evolved Packet Core (EPC) which includes a plurality offunctional/logical entities.

Although, for simplicity, a single base station 5 and two mobilecommunication devices 3 are shown, the E-UTRAN will generally comprise aplurality of base stations 5 and each base station 5 may serve one orany number of mobile communication devices 3 or other such communicationdevices.

MBMS Delivery System Architecture

As seen in FIG. 1 the communication system 1 comprises a systemarchitecture 1-1 for the delivery of multimedia broadcast/multicastservices (MBMS). The system architecture 1-1 for the delivery ofmultimedia broadcast/multicast services (MBMS) comprises aMulti-cell/Multicast Coordination Entity (MCE) 7, which forms part ofthe E-UTRAN. The MBMS delivery system architecture 1-1 also comprises aMobility Management Entity (MME) 9, an MBMS Gateway (MBMS-GW) 10, aBroadcast-Multicast Service Centre (BM-SC) 12 all of which form part ofthe core network 8. In operation, therefore, a content provider 13 isable to provide content, such as multimedia content, as an MBMS serviceusing the system architecture 1-1.

In the context of the MBMS delivery system architecture 1-1, the basestation 5 of the E-UTRAN is responsible for delivering MBMS data to adesignated MBMS service area efficiently.

The MCE 7 schedules the time/frequency resources on the radio interfaceand is responsible for coordinating multi-cell transmission where thecoverage area for a particular MBMS service includes multiple basestations 5. The MCE 7 is a logical entity which, in this embodiment, isphysically separate from the base station 5. The MCE 7 communicates withthe base station 5 via a control plane interface ‘M2’ and with the MME 9via a further control plane interface ‘M3’.

The MME 9 is a control node for the LTE access network and, in thecontext of MBMS delivery system architecture 1-1, provides a number ofMBMS support functions including session control of MBMS bearers andtransmission of session control messages (such as Session Start andSession Stop messages) towards the base station 5 of the E-UTRAN via theM3 interface. The MME 9 communicates with the MBMS-GW 10 using a furtherinterface ‘Sm’ via which the MME 9 receives MBMS service controlmessages and IP Multicast addresses for MBMS data reception.

The MBMS-GW 10 acts as an entry point for incoming broadcast/multicastdata. The MBMS-GW 10 is responsible for distributing data packets for aparticular MBMS service to base stations within the coverage area forthat MBMS service (e.g. an area covered by an MBMS Single FrequencyNetwork (MBSFN)), for example by IP multicast distribution of MBMS datapackets to the base station 5 through user plane interface ‘M1’. TheMBMS-GW 10 also implements MBMS session management (for example, byusing Session Start and Session Stop messages). The MBMS-GW 10communicates with the BM-SC via a user plane interface ‘SGi-mb’ and acontrol plane interface ‘SGmb’.

The BM-SC 12 is the source of the MBMS traffic and provides functionsfor MBMS user service provisioning and delivery. In this embodiment, theBM-SC 12 serves as an entry point for MBMS transmissions from thecontent provider 13, can be used to authorise and initiate MBMS BearerServices within the mobile network, and can be used to schedule anddeliver the MBMS transmissions, using the SGi-mb interface for MBMS datadelivery and the SGmb interface for control functions.

Unicast Delivery System Architecture

As seen in FIG. 2 the communication system 1 also comprises a systemarchitecture 1-2 for unicast delivery (also referred to herein aPacket-Switched Streaming Services (PSS) architecture). In the systemarchitecture 1-2 for unicast delivery, the core network 8 comprises theMME 9, a combined Serving Gateway and Packet Data Network-Gateway(SGW/PDN-GW) 15, a Policy and Charging Rules Function (PCRF) 19, and aHome Subscriber Server (HSS) 21. In operation, an operator 23 is able toprovide IP services, such as IP Multimedia Subsystem (IMS) services andPacket-switched Streaming (PSS) services, via the unicast deliverysystem architecture 1-2.

In the context of the unicast delivery system architecture 1-2, the basestation 5 of the E-UTRAN is responsible for establishing point-to-pointradio bearer resources towards each mobile communication device 3 andfor delivering data to it. The E-UTRAN communicates with the corenetwork via a logical interface ‘S1’ having a control plane part‘S1-MME’ and a user plane part ‘S1-U’.

In the context of the unicast delivery system architecture 1-2, the MME9 handles bearer management functions including dedicated bearerestablishment control towards each mobile communication device 3 via athe base station 5 of the E-UTRAN. The MME 9 communicates with the basestation 5 via the control plane part of the S1 interface (S1-MME) andwith the SGW part of the SGW/PDN-GW 15 via a further interface S11. TheMME 9 also communicates subscription and authentication data forauthenticating user access with the Home Subscriber Server (HSS) 21 viaa so called ‘S6a’ interface.

The SGW part of the SGW/PDN-GW 15 routes packet data to the base station5 of the E-UTRAN via the user plane part of the S1 interface S1-U. ThePDN-GW part of the SGW/PDN-GW 15 provides connectivity to the mobilecommunication device 3 for the connection to a PSS server (not shown)provided by the operator 23. The PDN-GW part of the SGW/PDN-GW 15communicates with the operator's network via another interface ‘SGi’.

The PCRF 19 is the policy and charging control element whichcommunicates with the PDN-GW part of SGW/PDN-GW 15 and the operator'snetwork via respective ‘Gx’ (or ‘S7’ in some versions of thearchitecture) and ‘Rx’ interfaces.

The HSS 21 is a network element that acts as a central repository ofsubscriber-specific authorizations and service profiles and preferencesfor an IMS network.

Adaptation of System Architectures

The various components of the communication system 1 of FIGS. 1 and 2are adapted to allow a dedicated radio access bearer (RAB) resource tobe setup towards an individual mobile communication device 3 for theprovision of a multimedia (MBMS) service to that mobile communicationdevice 3 using unicast communication. Specifically, the unicastcommunication is achieved, using the Packet-Switched Streaming Services(PSS) protocol, as an upper layer application function of the systemarchitecture 1-2 shown in FIG. 2. When E-UTRAN is used for the radioaccess, the RAB is called an E-RAB (EPS RAB).

The communication system 1 provides an MBMS service, to each mobilecommunication device 3 that indicates an interest in receiving that MBMSservice (referred to herein as an ‘interested’ mobile communicationdevice), using the unicast communication functionality when the numberof interested mobile communication devices 3 is below a predeterminedthreshold (referred to herein as a ‘broadcast’ threshold). When thenumber of interested mobile communication devices 3 is above thebroadcast threshold then the MBMS service is provided usingbroadcast/multicast communications in a conventional manner.

To facilitate accurate decision making relating to when unicast shouldbe used and when broadcast/multicast communication is more appropriate,the communication system 1 uses an improved mechanism for determiningthe number of interested mobile communication devices 3, within thecoverage area for a particular MBMS service. The counting mechanism notonly takes account of mobile communication devices 3 having an activeradio connection, but also takes account of mobile communication devices3 that are inactive (in idle mode). This is achieved by providing aprocedure via which idle mode mobile communication devices 3 canindicate their interest in receiving an MBMS service, can be counted forthe purposes of determining whether broadcast/multicast communication isappropriate, and can be identified for the purposes of setting upunicast radio bearers for the provision of the MBMS service of interest.

Accordingly, the communication system 1 described provides a number ofbenefits including greater accuracy when determining the number ofinterested users in the coverage area for a particular service. This inturn ensures that the decision-making process for determining when touse the networks broadcast/multicast functionality for providing an MBMSservice, and when not to, is greatly improved. Moreover, thecommunication system 1 also provides a mechanism via which mobilecommunication devices 3 can receive an MBMS service regardless of thenumber of mobile communication devices in the associated coverage thathave indicated an interest in receiving that MBMS service. Takingaccount of the number of idle mode mobile communication devices 3 isalso particularly beneficial because a user of an idle modecommunication device 3 may be more likely to want to receive aparticular MBMS service than a user of a mobile communication device 3that is active, for example, because the user of the active device isbusy making a voice call.

Mobile Communication Device

FIG. 3 schematically illustrates the main components of a mobilecommunication device 3 of FIGS. 1 and 2. As shown, the mobilecommunication device comprises a mobile telephone 3 includingtransceiver circuitry 323 which is operable to transmit signals to andto receive signals from the base station 5 via one or more antennae 325.As shown, the mobile telephone 3 also includes a controller 327 whichcontrols the operation of the mobile telephone 3 and which is connectedto the transceiver circuit 323 and to a loudspeaker 329, a microphone331, a display 333, and a keypad 335. The controller 327 operates inaccordance with software instructions stored within memory 337. Asshown, these software instructions include, among other things, anoperating system 339, an RRC module 341, and an application layer module343.

The RRC module 341 manages the reception, transmission, andinterpretation of radio resource control signalling communicated withthe base station 5. The RRC module 341 also controls RRC layerfunctionality in the mobile telephone 3 and manages signalling to andfrom an application layer. The application layer module 343 controlsapplication layer functionality of the mobile telephone 3 includingsignalling to and from the RRC layer.

Base Station

FIG. 4 is a block diagram illustrating the main components of the basestations 5 shown in FIGS. 1 and 2. As shown, the base station 5 includestransceiver circuitry 451, which is operable to transmit signals to, andto receive signals from, the mobile telephone 3 via one or more antennae453. Transceiver circuitry 451 is also coupled to an MCE interface 405,an SGW interface 407, an MBMS-GW interface 408 and an MME interface 410.The various interfaces 405, 407, 408 and 410 have corresponding logicalinterfaces (sometimes referred to as reference points) M2, S1-U, M1, andS1-MME as indicated in FIG. 4 in parenthesis.

The operation of the transceiver circuitry 451 is controlled by acontroller 457, in accordance with software stored in memory 459. Thesoftware includes, among other things, an operating system 461, acommunications module 419, an RRC module 463, an MBMS module 465, and aRAB management module 467.

The communications module 419 is operable to communicate: with the MCE 7via the MCE interface 405; with the SGW/PDN-GW 15 via the SGW interface407; with the MBMS-GW 10 via the MBNMS-GW interface 408; and with theMME via the MME interface 410. The RRC module 463 manages the reception,transmission, and interpretation of radio resource control signallingcommunicated with the mobile telephone 3. The MBMS module 465 managesthe reception, transmission, and interpretation MBMS related messagescommunicated with the MCE 7 and with the MBMS-GW 10. The RAB managementmodule 469 manages the reception, transmission, interpretation, andhandling of E-RAB setup related messages communicated with theSGW/PDN-GW 15 and with the MME 9.

Multi-Cell/Multicast Coordination Entity (MCE)

FIG. 5 shows an MCE 7 having a transceiver circuit 501 coupled to an eNBinterface 502 and an MME interface 503. The interfaces 502 and 503 havecorresponding logical interfaces (sometimes referred to as referencepoints) M2 and M3 as indicated in FIG. 5 in parenthesis.

A controller 507 is provided to control the transceiver circuit 501, andis coupled to a memory 509 comprising software including, among otherthings an operating system 511, a communications module 519 and an MBMSmanagement module 520. The communications module 519 is operable tocommunicate with the base station 5 via the eNB interface 502 and withthe MME via the MME interface 503. The MBMS management module 520manages the receipt and transmission of MBMS related signalling from andto the MME 9, and from and to the base station 5, in cooperation withthe communications module 519. The MBMS related signalling comprises,for example, session control signalling and other session managementsignaling and radio configuration for the multi-cell transmission modedata.

Mobility Management Entity (MME)

FIG. 6 shows an MME 9 having a transceiver circuit 601 coupled to an eNBinterface 602, an MME interface 603, an MCE interface 604, an SGWinterface 605, an MBMS-GW interface 608, and an HSS interface 610. Thevarious interfaces 602, 603, 604, 605, 608, 610 have correspondinglogical interfaces (sometimes referred to as reference points) S1-MME,S10, M3, S11, Sm and S6a as indicated in FIG. 6 in parenthesis.

A controller 607 is provided to control the transceiver circuit 601, andis coupled to a memory 609 comprising software including, among otherthings an operating system 611, a communications module 619, an MBMSmanagement module 620, and a unicast management module 621.

The communications module 619 is operable to communicate: with the basestation 5 via the eNB interface 602: with other MMEs (not shown) via theMME interface 603; with the MCE via the MCE interface 604; with the SGWpart of the SGW/PDN-GW 15 via the SGW interface 605; with the MBMS-GW 10via the MBMS-GW interface 608; and with the HSS 21 via the HSS interface610.

The MBMS management module 620 manages the receipt and transmission ofMBMS related signalling from and to the MCE 7, and from and to theMBMS-GW 10, in cooperation with the communications module 619. The MBMSrelated signalling comprises, for example: Session Start and SessionStop messages and related signalling; other MBMS service controlmessages; and the IP Multicast address for MBMS data reception; sentfrom the MBMS-GW 10 via the MBMS-GW (Sm) interface 608.

The unicast management module 621 manages the provision of unicastdelivery of MBMS services to the mobile communication devices 3including the setup and release of associated radio access bearers tothe mobile communication devices 3 for each MBMS service.

MBMS Gateway (MBMS-GW)

FIG. 7 shows an MBMS-GW 10 having a transceiver circuit 701 coupled toan eNB interface 702, an MME interface 705 and a BM-SC interface 710.The various interfaces 702, 705, 710 have corresponding logicalinterfaces (sometimes referred to as reference points) M1, SGmb/SGi-mb,and Sm as indicated in FIG. 7 in parenthesis.

A controller 707 is provided to control the transceiver circuit 701, andis coupled to a memory 709 comprising software including, among otherthings, an operating system 711, a communications module 719 and an MBMSmanagement module 720. The communications module 719 is operable tocommunicate: with the base station 5 via the eNB interface 702: with theMME via the MME interface 705; and with the BM-SC via the BM-SCinterface 710.

The MBMS management module 720 manages the distribution of MBMS datapackets to base stations 3 within the MBSFN, for example by IP multicastof the MBMS data packets to the eNB 5 through the eNB (M1) interface702. The MBMS management module 720 is also responsible for MBMS sessionmanagement, for example, by transmitting the Session Start and SessionStop messages to the MME 9.

Broadcast-Multicast Service Centre (BM-SC)

FIG. 8 shows a BM-SC 12 having a transceiver circuit 801 coupled to anMBMS-GW interface 803 and a content provider interface 810. The MBMS-GWinterface 803 has corresponding logical user plane interface SGi-mb andcontrol plane interface SGmb (sometimes referred to as referencepoints).

A controller 807 is provided to control the transceiver circuit 801, andis coupled to a memory 809 comprising software including, among otherthings, an operating system 811, a communications module 819 and an MBMSmanagement module 820.

The communications module 819 is operable to communicate MBMS data tothe MBMS gateway via the user plane interface (SGi-mb) part of interface803 and control signalling via the control plane interface (SGmb) partof interface 803. The communications module 819 is also operable toreceive content from the content provider 13 via the content providerinterface 810.

The MBMS management module 820 manages the MBMS functions of the BM-SC12 including the initiation of MBMS traffic from the content provider13, user service provisioning, and delivery of MBMS data via the userplane interface (SGi-mb). The MBMS management module 820 also handlesauthorisation and initiation of MBMS bearer services and scheduling ofthe MBMS transmissions.

Serving Gateway/Packet Data Network Gateway (SGW/PDN-GW)

FIG. 9 shows a combined SOW/PDN-GW 15 having a transceiver circuit 901coupled to an eNB interface 902, an MME interface 903, an operatornetwork interface 905, and a PCRF interface 910. The various interfaces902, 903, 905, 910 have corresponding logical interfaces (sometimesreferred to as reference points) S1-U, S11, SGi, and S7/Gx as indicatedin FIG. 9 in parenthesis.

A controller 907 is provided to control the transceiver circuit 901, andis coupled to a memory 909 comprising software including, among otherthings, an operating system 911, a communications module 919, an SGWmodule 920, and a PDN-GW module 921, and a PSS management module 922.The communications module 919 is operable to handle SGW relatedcommunications with the base station 5 via the eNB interface 902 andwith the MME 9 via the MME interface 903. The communications module 919is also operable to handle PDN-GW related communications with theoperator network via the operator network interface 905 and with thePCRF 19 via the PCRF interface 910.

The SGW module 920 provides the functions of the serving gateway part ofthe SGW/PDN-GW 15 and the PDN-GW module 921 provides the functions ofthe PDN gateway part of the SGW/PDN-GW 15. The PSS management modulemanages the Packet-Switched Streaming Services functions of theSGW/PDN-GW 15 in cooperation with the SGW module 920 and the PDN-GWmodule 921.

MBMS Service Provision via Unicast and/or Broadcast/Multicast—Overview

FIG. 10 is a high-level flow chart illustrating a procedure implementedby the communication system 1 to provide selectively an MBMS service byunicast and/or by broadcast/multicast in dependence on the number ofmobile communication devices 3 interested in receiving that MBMSservice.

As seen in FIG. 10 the procedure begins with the initiation of a newMBMS service (S1) by the BM-SC 12 requesting the start of an associatedMBMS session via the MBMS-GW 10 for a particular coverage area. Beforethe requested MBMS session is initiated, a counting procedure isundertaken to determine the number of mobile communication devices 3indicating an interest (‘interested mobile communication devices’) inreceiving the requested MBMS service (S2). The counting procedureincludes counting mobile communication devices 3 that are normally inidle mode (S2a) and mobile communication devices 3 that are in an active(or ‘connected’) mode (S2b). Once the total number of interested mobilecommunication devices 3 in the coverage area has been counted, the totalis compared to a predetermined threshold (‘t_(BM)’) above whichprovision of the MBMS service via broadcast/multicast is considered tobe viable (S3). If the total number of interested mobile communicationdevices 3 is found to be below the threshold ‘t_(BM)’, then a procedureto provide the MBMS service, via unicast, to each interested mobilecommunication device 3 is activated (S4). Otherwise, if the total numberof interested mobile communication devices 3 is found to be above thethreshold ‘t_(BM)’, then a procedure to provide the MBMS service viabroadcast/multicast is initiated (S6).

The procedure to activate the MBMS service via unicast comprises aninitial procedure (S4a) followed by a RAB setup procedure (S4b). Theinitial procedure (S4a) involves the MCE 7 informing the BM-SC 12, viathe MME 9 and the MBMS-GW 10 that there are insufficient interestedmobile communication devices 3 to warrant broadcast/multicast delivery.The RAB setup procedure (S4b) involves setup of a respective radioaccess bearer for delivering the MBMS service to each interested mobilecommunication device 3 via unicast.

After delivery via unicast or broadcast/multicast is setup, the countingand comparison procedure is periodically repeated (S5-1/S5-2) todetermine if the number of interested mobile communication devices 3 inthe coverage area for the MBMS service has changed significantly. Whenthe MBMS service is being delivered via unicast and the number ofinterested users is determined to have increased above the thresholdt_(BM), delivery via broadcast/multicast is initiated (S6). Otherwise,if the number of interested users remains below the threshold t_(BM),delivery of the MBMS service via unicast is maintained for each mobilecommunication device 3 already receiving it, and is activated for anyinterested mobile communication devices 3 that are not already receivingit (S4). When the MBMS service is being delivered viabroadcast/multicast and the number of interested users is determined tohave decreased below the threshold t_(BM), delivery viabroadcast/multicast is deactivated (S7) and delivery of the MBMS servicevia unicast is activated (S6) for each interested mobile communicationdevices 3 remaining in the coverage area. Otherwise, if the number ofinterested users remains above the threshold t_(BM), delivery of theMBMS service via broadcast/multicast is maintained.

There are a number of different ways in which the various stages of theprocedure of FIG. 10 may be implemented including: a network centricapproach in which the network initiates the setup of each radio accessbearer for the provision of the MBMS service to a respective mobilecommunication device using unicast communication; and a so called ‘UE’centric approach in which each mobile communication device wishing toreceive the MBMS service initiates the setup the radio access bearerrequired for the provision of the MBMS service to it via unicastcommunication.

The present embodiment makes use of a network centric approach whichwill now be described in more detail.

Network Centric Approach

FIGS. 11 to 18 illustrate, in more detail, the steps (S1 to S7) of theprocedure of FIG. 10 for counting mobile communication devices, and forproviding the MBMS service via unicast and/or broadcast/multicastaccordingly according to the present embodiment. The procedureillustrated in FIGS. 11 to 18 is a network centric approach in which thenetwork is responsible for initiating setup of unicast communication.

For simplicity, in FIGS. 11 to 18, the actions of the MBMS-GW and theBM-SC are combined.

(S1) MBMS Session Service Start

FIG. 11 is a simplified timing diagram illustrating the MBMS sessionservice start phase (S1) of the procedure of FIG. 10 in more detail.

As seen in FIG. 11 the BM-SC 12 initiates an MBMS session via theMBMS-GW 10. To request initiation of the MBMS service, the MBMS-GW 10sends an MBMS Session Start Request to the MME 9 effectively requestinginitiation of a broadcast/multicast session for delivery of the MBMSservice. The MBMS Session Start Request comprises information including(among other information):

-   -   an MBMS Service ID for identifying the MBMS service to which the        request relates;    -   an MBMS session ID for identifying the MBMS session to be used        to provide the MBMS service;    -   an Evolved Packet System (EPS) Radio Access Bearer (RAB) Quality        of Service information element identifying, for example, QoS        parameters such as end to end delay, bit error rates etc;    -   an MBMS Service Area identifier identifying the area (e.g. a        cell or group of cells) in which the MBMS session is made        available;    -   an IP Multicast address identifying the IP address from which        the MBMS data is distributed; and

an IP source address.

The MBMS Session Start Request is forwarded by the MME 9 to the MCE 7.In this embodiment the forwarded MBMS Session Start Request includesinformation for notifying the MCE 7 that counting of the interestedmobile communication devices 3 is required before delivery of the MBMSservice via broadcast/multicast can be allowed. In response to the MBMSSession Start Request, therefore, the MCE 7 determines that theprocedure for counting the interested mobile communication devices 3should be initiated for the MBMS service to which the MBMS Service IDrelates.

To initiate the counting procedure, the MCE 7 sends an MBMS ServiceCounting Request to each base station 5 in the coverage area (e.g. theMBSFN area) to inform the base station 5 that counting should commencefor the identified MBMS Service. The MBMS Service Counting Requestincludes the identity of the MBMS Service (MBMS Service ID) and the MBMSservice area (MBMS Service Area).

On receipt of the MBMS Service Counting Request each base station 5 inthe coverage area indicates to the mobile communication devices 3 itserves that counting is required to receive the MBMS service. In thisembodiment, the base station 5 provides this indication in SystemInformation, which is periodically broadcast to the mobile communicationdevices. Thus, the mobile communication device 3 is able to determinethat it is required to expressly indicate to the base station 5 that itis interested in receiving the MBMS service.

(S2) Count Mobile Communication Devices ‘Interested’ in Receiving theMBMS Service

FIGS. 12 and 13 are simplified timing diagrams illustrating, in moredetail, the phase of the procedure (S2) shown in FIG. 10, for countingthe mobile communication devices 3 that are interested in receiving aparticular MBMS Service.

Specifically, FIG. 12 illustrates the part of the procedure (S2a) forcounting the mobile communication devices 3 that are in idle mode, andFIG. 13 illustrates the part of the procedure (S2b) for counting themobile communication devices 3 that are active.

(S2a) Idle Mobile Communication Device Count

As seen in FIG. 12, in this embodiment, after the counting procedure hasbeen initiated, when a mobile communication device 3 in idle mode isinterested in receiving one or more MBMS services, the mobilecommunication device 3 initiates a temporary RRC connection bygenerating and sending an RRC Connection Request. The base station 5responds by sending an RRC Connection Setup message to allow the mobilecommunication device 3 to setup the RRC connection. On setup of theconnection, the mobile communication device 3 generates an RRCConnection Setup Complete message, including a Network ID and aregistered core network ID, to indicate successful setup of the RRCconnection and sends it to the base station 5.

However, in addition to the Network ID and a registered core network ID,the mobile communication device 3 also incorporates a NULL Non AccessStratum (NAS) message (a message in which a NAS Information Element hasa length set to zero) into the RRC Connection Setup Complete message,when requesting the RRC connection establishment.

In parallel, after the counting procedure has been initiated by the basestation 5 (in response to receipt of the MBMS Service Counting Requestin phase (1)), the base station 5 begins to monitor RRC signalling, fromthe mobile communication devices 3 it serves, for the presence of NULLNAS messages. On receipt of a message incorporating a NULL NAS messagethe base station 5 determines that the mobile communication device 3from which it has received the message has initiated the RRC connectionfor the purposes of the MBMS counting procedure and accordingly, in thisembodiment, does not progress the connection further into the network(e.g. by generating further connection setup messages and sending themto the MME 9). In this manner this embodiment has the benefit ofreducing signalling.

At this stage, the base station 5 does not yet know the identity of theMBMS Service that the mobile communication device 3 is interested inbecause there may be several MBMS Services for which counting isrequired. Accordingly, the base station 5 waits for further signallingfrom the mobile communication device 3.

In order to inform the base station 5 of the MBMS service for which thetemporary RRC connection was initiated, the mobile communication device3 generates a RRC MBMS Counting Report incorporating an MBMS Service IDfor identifying the MBMS service which the mobile communication device 3is interested in receiving, and sends it to the base station 5. It willbe appreciated that, if the mobile communication device 3 is interestedin receiving more than one MBMS service from among those for which acounting procedure is being undertaken, then the mobile communicationdevice 3 includes all the interested MBMS services

On receipt of the RRC MBMS Counting Report, the base station 5 storesinformation identifying the mobile communication device 3 from which itreceived the message, in association with the identity of MBMS servicefor which the mobile communication device 3 has indicated an interest.In this manner, the base station 5 compiles a ‘count’ list of the mobilecommunication devices 3 that were in the idle mode when the MBMS servicewas initiated, without requiring setup of a full RRC connection. Thebase station 5 can then release the temporary (and partial) RRCconnection by sending an RRC Connection Release message to the mobilecommunication device 3.

(S2b) Active Mobile Communication Device Count

As seen in FIG. 13, after the counting procedure has been initiated,when a mobile communication device 3 in active mode is interested inreceiving one or more MBMS services, the mobile communication device 3indicates its interest in receiving a particular MBMS service by sendingan RRC MBMS Counting Report incorporating the identity of that MBMSservice as part of the already established RRC connection.

On receipt of the RRC MBMS Counting Report, the base station 5 storesinformation identifying the mobile communication device 3 from which itreceived the message, in association with the identity of MBMS servicefor which the mobile communication device 3 has indicated an interest.In this manner, the base station 5 includes mobile communication devices3 with an active connection in the count list for that MBMS servicealong with any interested idle mode mobile communication devices 3. Thebase station 5 does not need to release the RRC connection in this casebecause it is in use for other purposes by the active mobilecommunication device 3.

(S3) Comparison with Threshold

FIG. 14 is a simplified timing diagram illustrating the thresholdcomparison phase (S3) of the procedure of FIG. 10 in more detail.

As seen in FIG. 14, after the mobile communication devices 3 served by abase station 5 have indicate their interest in receiving an MBMS serviceand the base station 5 has collated the results in the count list, thebase station 5 generates the resulting ‘counting result’ which, in thisembodiment, comprises a list of identifiers for the interested mobilecommunication devices 3, and incorporates this into an MBMS ServiceCounting Response message, in association with the identity of the MBMSservice (MBMS Service ID) to which the list relates, and sends the MBMSService Counting Response message to the MCE 7.

On receipt of MBMS Service Counting Response messages from all the basestations 5 in the coverage area (e.g. MBSFN area) for the MBMS serviceto which the messages relate, the MCE 7 determines the total number ofinterested mobile communication devices 3, including both idle mode andactive mobile communication devices 3, and compares the result with thepredetermined broadcast threshold t_(BM).

(S4) MBMS Service via Unicast—Activation

FIGS. 15 and 16 are simplified timing diagrams illustrating the MBMSservice via unicast activation phase (S4) of the procedure of FIG. 10 inmore detail. Specifically, FIG. 15 illustrates an initial part of theunicast activation phase (S4) in which the unicast delivery isinitiated, and FIG. 16 illustrates a further part of the unicastactivation phase (S4) in which the radio access bearers for unicastcommunication are setup.

(S4a) Initial Procedure

As seen in FIG. 15, when the comparison performed by the MCE 7determines that the total number of interested mobile communicationdevices 3, including both idle mode and active mobile communicationdevices 3, is less than the predetermined broadcast threshold t_(BM),the MCE 7 generates a diagnostic response message and sends it to theMME 9. The diagnostic response message comprises an MBMS Session StartResponse message incorporating the identity of the MBMS service to whichit relates and information indicating a so called ‘failure cause’ to bethat the ‘number of interested UEs is under a threshold for broadcastdelivery’.

The MME 9 forwards the MBMS Session Start Response message to MBMS-GW 10which, in turn informs the BM-SC 12. Accordingly, the BM-SC 12 is ableto establish that resources will be setup for delivering the MBMSservices via unicast directly to each interested mobile communicationdevice 3.

Further to sending the MBMS Session Start Response message indicating afailure to setup delivery using broadcast/multicast, the MCE 7 sends thelist of interested mobile communication devices 3 for the MBMS serviceto the MME 9, so that the MME 9 can request each base station 5 to setupa radio bearer towards each interested mobile communication device 3that the base station 5 serves. Specifically, the MCE 7 generates anMBMS Session Information Indication incorporating the identity of theMBMS service and a list of Evolved Packet System UE temporary identities(EPS UE temporary IDs) including an ID for each interested mobilecommunication device 3.

(S4b) Network Initiated RAB Setup Procedure

As seen in FIG. 16, after sending the MBMS Session InformationIndication, the MME 9 triggers the setup of radio bearers for providingthe unicast delivery of the MBMS service. In this embodiment, thisprocess is initiated by sending a message requesting the setup of anE-UTRAN radio access bearer (E-RAB Setup Request) to base station 5 overthe MME-S1 interface 602. The E-RAB Setup Request includes, among otherthings: an identifier for the E-RAB being setup (E-RAB ID); EPS RadioAccess Bearer Quality of Service information; an NAS messageincorporating an EPS bearer context activation request; the identity ofthe MBMS service (MBMS service ID); and the IP multicast address for theMBMS service.

Thanks to the presence of the IP multicast address received in the RadioAccess Bearer Setup Request from the MME 9, the base station 5 is ableto perform a joining operation, if appropriate (e.g. if not previouslycarried out for the MBMS service), for each interested mobilecommunication device 3. The joining operation is the process by which aparticular user ‘joins’ (or becomes a member of) a particular multicastgroup, for example by the user indicating to the network that he/shewants to receive multicast mode data for a specific MBMS bearer service.

The base station 5 generates an RRC Connection Reconfiguration messageincorporating an identity of the radio bearer (Radio Bearer ID), theidentity of the MBMS service (MBMS service ID), and an NAS message, andsends it to the mobile communication device to initiate configuration ofthe radio bearer at the mobile communication device 3. Onceconfiguration of the radio bearer is complete, the mobile communicationdevice 3 generates an RRC Connection Reconfiguration Complete messageand sends it to the base station 5 to indicate completion.

To complete the radio access bearer setup part (S4b) of the unicastactivation procedure (S4) the base station 5 generates an E-RAS SetupResponse message and sends it to the MME 9. The E-RAB Setup Responsemessage incorporates respective identifiers for uniquely identifying themobile communication device 3 over the S1 interface within the basestation 5 and over the S1 interface within the MME 9 (MME UE S1AP ID andeNB UE S1AP ID) and the identity of the E-UTRAN radio access bearer(E-RAB ID).

(S5-1/S6) MBMS Service via Broadcast/Multicast Activation (DuringUnicast provision)

FIG. 17 is a simplified timing diagram illustrating the MBMS service viabroadcast/multicast activation phase (S6) of the procedure of FIG. 10 inmore detail following the periodic recount of the number of interestedmobile communication devices 3 (both idle and active) and associatedthreshold comparison (S5-1). Specifically, FIG. 17 illustrates asituation in which the broadcast/multicast activation phase followsdelivery of the MBMS service via unicast (e.g. the periodicrecount/comparison (S5-1) has indicated that the number of interestedmobile communication devices 3 (both idle and active) has risen abovethe broadcast threshold t_(BM)).

While the service is being delivered via unicast transmission, the MME 9provides an indication to the MCE 7, so that the MCE 7 knows to performa periodic recount of interested mobile communication devices for agiven MBMS service. Specifically, an MBMS Session Start Request with adedicated information so called “unicast delivery ongoing” can be used.

As seen in FIG. 17, when the periodic recount/comparison (S5-1)indicates that the number of interested mobile communication devices 3has risen above the broadcast threshold t_(BM), the MCE 7 initiatesprovision of the MBMS service via broadcast/multicast. The delivery ofthe MBMS service via broadcast/multicast is setup using conventionalprocedures (e.g. the procedures defined in the current version of therelevant 3GPP standard) which a skilled person would readily understand,and which are therefore not described in detail here.

In this embodiment, after delivery of the MBMS service viabroadcast/multicast has been setup (which can be indicated to the MME 9using a MBMS Session Start Indication including the MBMS service), theMME 9 initiates deactivation of the direct unicast delivery of the MBMSservices by unicast to individual mobile communication devices 3. Thisis possible because, in this network centric approach, the MME 9advantageously knows which mobile communication devices 3 have a unicastbearer for the MBMS service.

In this embodiment, the MME 9 triggers the deactivation of the directunicast delivery of the MBMS services by generating a radio bearerrelease request (e.g. an E-RAB Release Command incorporating a listidentifying each radio access bearer to be released) and sending it tothe base station 5. In response to the radio bearer release request, thebase station 5 and each affected mobile communication device 3 cooperateto release the associated MBMS delivery radio bearer, after which thebase station 5 acknowledges completion by sending a completion message(E-RAB Release Complete) to the MME 9.

(S5-2/S7) MBMS Service via Broadcast/Multicast Deactivation

FIG. 18 is a simplified timing diagram illustrating the MBMS service viabroadcast/multicast deactivation phase (S7) of the procedure of FIG. 10in more detail following the periodic recount of the number ofinterested mobile communication devices 3 (both idle and active) andassociated threshold comparison (S5-2). Specifically, FIG. 18illustrates a situation in which the broadcast/multicast deactivationphase (S7) follows a periodic recount/comparison (S5-2) indicating thatthe number of interested mobile communication devices 3 (both idle andactive) has fallen from above, to below the broadcast threshold t_(BM).

As seen in FIG. 18, when the periodic recount/comparison (S5-2)indicates that the number of interested mobile communication devices 3has fallen below the broadcast threshold t_(BM), the MCE 7 initiatesdeactivation of the MBMS service via broadcast/multicast. The deliveryof the MBMS service via broadcast/multicast is deactivated usingconventional procedures (e.g. the procedures defined in the currentversion of the relevant 3GPP standard) which a skilled person wouldreadily understand, and which are therefore not described in detailhere.

Deactivation of delivery of the MBMS service via broadcast/multicast isindicated by the MCE 7 to MME 8 using a MBMS Session Stop Request. TheMBMS Session Stop Request includes: a dedicated information elementindicating the cause of the stop request to be “number of interested UEsunder a threshold for broadcast delivery” and a MBMS Session InformationIndication including the MBMS service ID and the list of EPS UEtemporary IDs. After delivery of the MBMS service viabroadcast/multicast has been deactivated, the MME 9 initiates(re)activation of the direct unicast delivery of the MBMS services byunicast to individual mobile communication devices 3 (e.g. as describedabove for the MBMS service via unicast activation phase (S4)).

Summary—Network Centric Approach

In summary, therefore, using the network centric approach, the MME 9triggers the delivery of the MBMS service via unicast further toindication of relevant interested mobile communication devices 3 foreach MBMS service from the MCE 7. The MCE 7 effectively informs the MME9 when broadcast/multicast transmission of an MBMS service cannot be setup because of the low number of interested mobile communication devices3 in some MBSFN areas of the MBMS service area. The IP multi castaddress and the MBMS service ID are included in the radio bearer setuprequest from the MME 9 to the LTE radio access network. The MBMS serviceID is included in the radio bearer setup request from the LTE radioaccess network to the mobile communication device 3. Thus, by knowingthe radio bearer that is associated with the MBMS service delivered viaunicast, the MME 9 is able to trigger a release of that bearer when itis notified by the MCE 7 that the broadcast/multicast delivery of theMBMS service has been activated.

Network Centric Approach—Possible Variations

As those skilled in the art will appreciate, there are a number ofpossible variations that could be made to the network centric approachdescribed above whilst still benefiting from the inventions embodiedtherein. A number of these will now be described, by way of exampleonly, to illustrate the flexibility of the network approach to beadapted, depending on requirements, whilst still providing the same orsimilar benefits.

(S2a) Idle Mode mobile communication device Counting—Variation 1

FIG. 19 is a simplified timing diagram illustrating a first possiblevariation of the idle mode part (S2a) of the counting phase (S2) of FIG.12 that might be used in a further embodiment.

As seen in FIG. 19, as described for the previous embodiment, after thecounting procedure has been initiated, when a mobile communicationdevice 3 in idle mode is interested in receiving one or more MBMSservices, the mobile communication device 3 initiates a temporary RRCconnection by generating and sending an RRC Connection Request. The basestation 5 responds by sending an RRC Connection Setup message to allowthe mobile communication device 3 to setup the RRC connection. On setupof the connection the mobile communication device 3 generates an RRCConnection Setup Complete message, including a Network ID and aregistered core network ID, to indicate successful setup of the RRCconnection, and sends the generated message to the base station 5.

As described for the previous embodiment, in addition to the Network IDand a registered core network ID, the mobile communication device 3 alsoincorporates a NULL Non Access Stratum (NAS) message (a message in whicha NAS Information Element has a length set to zero) into the RRCConnection Setup Complete message, when requesting the RRC connectionestablishment.

Unlike the previous embodiment, however, the base station 5 does notmonitor RRC signalling for the presence of NULL NAS messages. Instead,the base station treats the RRC connection as normal (according to thecurrent 3GPP standards) by generating an Initial UE Message and sendingit to the MME 9. The Initial UE Message incorporates an identifier (e.g.an application identifier) for uniquely identifying the mobilecommunication device 3 over S1 interface within the base station 5 (eNBUE S1AP ID), a further ‘temporary identifier’ (UE temporary ID), and theNAS message. However, it will be appreciated, that unlike a conventionalInitial UE Message, the NAS Message carried by the Initial UE Message inthis case is a NULL NAS Message having an NAS PDU set to zero.

In response to the Initial UE Message, and more specifically the NULLNAS message carried by it, the MME 9 responds by generating, in thisembodiment, a context release message (UE S1 Context Release Command) oranother appropriate S1 message and sending it to the base station 5,because the MME 9 is unable to handle the NULL NAS message. The UE S1Context Release Command incorporates an indication (a ‘cause IE’) thatthe reason for the release is the presence of the NULL NAS Message inthe Initial UE Message (cause IE=NULL NAS message). On the receipt ofthe context release message, the base station 5 infers that the originalRRC connection request was sent for the purposes of the MBMS countingprocedure.

At this stage, the base station does not yet know the identity of theMBMS Service that the mobile communication device 3 is interested inbecause there may be several MBMS Services for which counting isrequired. Accordingly, the base station 5 waits for further signallingfrom the mobile communication device 3.

In order to inform the base station 5 of the MBMS service for which thetemporary RRC connection was initiated, the mobile communication device3 generates a RRC MBMS Counting Report incorporating an MBMS Service IDfor identifying the MBMS service which the mobile communication device 3is interested in receiving, and sends it to the base station 5.

On receipt of the RRC MBMS Counting Report, the base station 5 storesinformation identifying the mobile communication device 3 from which itreceived the message, in association with the identity of MBMS servicefor which the mobile communication device 3 has indicated an interest.In this manner, the base station 5 compiles a ‘count’ list of the mobilecommunication devices 3 that were in the idle mode when the MBMS servicewas initiated, without requiring setup of a full RRC connection. Thebase station 5 can then release the temporary (and partial) RRCconnection by sending an RRC Connection Release message to the mobilecommunication device 3.

Accordingly, this embodiment has the benefit that it avoids the need forthe base station to be adapted to screen RRC Connection Requests forNULL NAS messages, albeit at the expense of an increased signallingoverhead.

(S2a) Idle Mode mobile communication device Counting—Variation 2

FIG. 20 is a simplified timing diagram illustrating another possiblevariation of the idle mode part (S2a) of the counting phase (S2) of FIG.12 that might be used in a further embodiment.

As seen in FIG. 20, as described for the previous embodiments, after thecounting procedure has been initiated, when a mobile communicationdevice 3 in idle mode is interested in receiving one or more MBMSservices, the mobile communication device 3 initiates a temporary RRCconnection by generating and sending an RRC Connection Request. The basestation 5 responds by sending an RRC Connection Setup message to allowthe mobile communication device 3 to setup the RRC connection. On setupof the connection, the mobile communication device 3 generates an RRCConnection Setup Complete message, including a Network ID and aregistered core network ID, to indicate successful setup of the RRCconnection, and sends the generated message to the base station 5.

Like the previous embodiments, the mobile communication device 3includes a Network ID, a registered core network ID, and a NULL NonAccess Stratum (NAS) message in the RRC Connection Setup Completemessage. Unlike the previous embodiments, however, the mobilecommunication device 3 also includes an MBMS Counting Report thatincorporates an MBMS Service ID (or a list of such IDs), for identifyingthe MBMS service(s) that the mobile communication device 3 is interestedin receiving.

On receipt of the RRC Connection Setup Complete message, the basestation 5 identifies the MBMS service(s) listed in the MBMS CountingReport incorporated within the RRC Connection Setup Complete anddetermines that the RRC connection request was sent for the purposes ofthe MBMS counting procedure.

Moreover, since the base station 5 knows the identity of the MBMSService(s) that the mobile communication device 3 is interested in, thebase station 5 does not have to wait for further signalling from themobile communication device 3. Thus, the base station 5 can storeinformation identifying the mobile communication device 3 from which itreceived the message, in association with the identity of MBMSservice(s) for which the mobile communication device 3 has indicated aninterest. In this manner, the base station 5 compiles a ‘count’ list ofthe mobile communication devices 3 that were in the idle mode when theMBMS service was initiated, without requiring setup of a full RRCconnection. The base station 5 can then release the temporary (andpartial) RRC connection by sending an RRC Connection Release message tothe mobile communication device 3.

Accordingly, this variation advantageously avoids the need forsignificant further signalling, for example, by avoiding the need tosend any NAS message to the EPS core network 8.

(S4b) Network Initiated RAB Setup Procedure—Variation

FIG. 21 is a simplified timing diagram illustrating a possible variationof the network initiated RAB setup part (S4b) of the MBMS service viaunicast activation phase (S4) of FIG. 16, which might be used in afurther embodiment.

As seen in FIG. 21, like the first embodiment, after sending the MBMSSession Information Indication, the MME 9 triggers the setup of radiobearers for providing the unicast delivery of the MBMS service. However,unlike the first embodiment, in this variation, the process begins bygenerating a message for triggering bearer setup via the SGW/PDN-GW 15(e.g. a Bearer Resource Command or Create Session Request) and sendingthe generated message to the SGW/PDN-GW 15. The message for triggeringbearer setup incorporates appropriate information such as, for example,an identifier of the mobile communication device 3 (UE permanent ID), anidentifier for the radio access bearer (Linked EPS Bearer ID), andaccess point identifier (APN—e.g. the IP multicast address), and/or(MBMS) Quality of Service Information.

In response to receiving the message for triggering bearer setup, theSGW/PDN-GW 15 responds by generating an associated response message forsetting up the bearers for unicast procedure in accordance with aconventional PSS procedures (e.g. as defined in the relevant 3GPPstandards) as would readily be understood be a skilled person. Thismessage is then sent to the MME 9 to allow the MME 9 to co-ordinate therest of the procedure.

The MME 9 generates and sends a message requesting the setup of anE-UTRAN radio access bearer (E-RAB Setup Request) to base station 5. Thebase station 5 generates an RRC Connection Reconfiguration messageincorporating an identity of the radio bearer (Radio Bearer ID) and anNAS message, and sends it to the mobile communication device to initiateconfiguration of the radio bearer at the mobile communication device 3.Once configuration of the radio bearer is complete, the mobilecommunication device 3 generates an RRC Connection ReconfigurationComplete message and sends it to the base station 5 to indicatecompletion.

To complete the radio access bearer setup part (S4b) of the unicastactivation procedure (S4) the base station 5 generates an E-RAB SetupResponse message and sends it to the MME 9. The E-RAB Setup Responsemessage incorporates respective identifiers for uniquely identifying themobile communication device 3 over the S1 interface within the basestation 5 and over the S1 interface within the MME 9 (MME UE S1AP ID andeNB UE S1AP ID) and the identity of the E-UTRAN radio access bearer(E-RAB ID).

Accordingly, in this variation, the MME 9 triggers the new BearerResource allocation by signalling towards the Serving/PDN Gateways 15rather than the base station 5. This variation advantageously makes useof key features of a legacy EPS architecture to provide unicast usingPSS thereby providing for improved backwards compatibility.

UE Centric Approach

FIGS. 22 and 23 illustrate, in more detail, key steps of the procedureof FIG. 10 for counting mobile communication devices, and for providingthe MBMS service via unicast and/or broadcast/multicast according toanother embodiment. The procedure illustrated in FIGS. 22 and 23 is a UEcentric approach in which the mobile communication device 3 isresponsible for initiating setup of unicast communication.

In this embodiment, the UE centric approach, the MBMS session servicestart phase (S1), the counting phase (S2, S2a, S2b), and the thresholdcomparison phase (S3) proceed essentially as described for the firstembodiment for FIGS. 11 to 14, although it will be appreciated that thevariations to the counting phase may be employed in other embodiments.

In this embodiment, however, a variation on the unicast activation phase(S4) is employed.

(S4) MBMS Service via Unicast—Activation (UE Centric Approach)

FIG. 22 is a simplified timing diagram illustrating the variation of theunicast activation phase (S4) for the UE centric approach to theimplementation of the procedure in FIG. 10, in more detail.

(S4a) Initial Procedure (UE Centric Approach)

As seen in FIG. 22, when the comparison performed by the MCE 7determines that the total number of interested mobile communicationdevices 3, including both idle mode and active mobile communicationdevices 3, is less than the predetermined broadcast threshold t_(BM),the MCE 7 generates a ‘failure indicating’ response message and sends itto the MME 9. The diagnostic response message effectively indicates, tothe MME 9, that the attempt to setup delivery of the MBMS service viabroadcast/multicast has failed. The response message comprises an MBMSSession Start Response message incorporating the identity of the MBMSservice to which it relates and information indicating the reason forthe failure to be that the ‘number of interested UEs is under athreshold for broadcast delivery’.

The MME 9 forwards the MBMS Session Start Response message to MBMS-GW10, which in turn informs the BM-SC 12. In this embodiment, the BM-SCestablishes that the resources for establishing unicast delivery of theMBMS service will be setup using the PSS architecture 1-2.

At this stage, unlike the previous embodiments, delivery of the MBMSservice is not initiated by the network, instead it is initiated by eachmobile communication device 3 wishing to receive the MBMS service.

(S4b) UE Initiated RAB Setup Procedure (UE Centric Approach)

Each mobile communication device 3 interested in receiving a particularMBMS service, in this embodiment, monitors for setup of MBMS servicedelivery via broadcast/multicast by monitoring the MBMS control channelfor the corresponding MBMS service ID.

When the MBMS service is not made available, the RRC layers of themobile communication device 3 detect the absence of the expected MBMSService ID on the control channel, when the counting procedure hasstopped, and signals the absence to the application layers.

Upon receipt of an indication from the radio layers that the MBMSService ID is not present, the application layers in the mobilecommunication device 3 initiate setup of the radio bearers for unicastdelivery of the service via the PSS architecture 1-2 using conventionallegacy mechanisms (e.g. as described in the relevant 3GPP standards).

(S5-1/S6) MBMS Service via Broadcast/Multicast Activation (duringUnicast provision—UE Centric Approach)

FIG. 23 is a simplified timing diagram illustrating the MBMS service viabroadcast/multicast activation phase (S6) for the UE centric approach tothe implementation of the procedure in FIG. 10, in more detail. Theactivation phase (S6) is illustrated following the periodic recount ofthe number of interested mobile communication devices 3 (both idle andactive) and associated threshold comparison (S5-1). Specifically, FIG.23 illustrates a situation in which the broadcast/multicast activationphase follows delivery of the MBMS service via unicast (e.g. theperiodic recount/comparison (S5-1) has indicated that the number ofinterested mobile communication devices 3 (both idle and active) hasrisen above the broadcast threshold t_(BM)).

As seen in FIG. 23, when the periodic recount/comparison (S5-1)indicates that the number of interested mobile communication devices 3has risen above the broadcast threshold t_(BM), the MCE 7 initiatesprovision of the MBMS service via broadcast/multicast. The delivery ofthe MBMS service via broadcast/multicast is setup using conventionalprocedures (e.g. the procedures defined in the current version of therelevant 3GPP standard) which a skilled person would readily understand,and which are therefore not described in detail here.

Unlike the network centric approach, however, after delivery of the MBMSservice via broadcast/multicast has been setup, the MME 9 does notinitiate deactivation of the direct unicast delivery of the MBMSservices by unicast to individual mobile communication devices 3 becausethe MME 9 does not know which mobile communication devices 3 have aunicast bearer set up. Accordingly, mobile communication devices 3already receiving the MBMS service via unicast continue to do sosimultaneously with delivery of the MBMS service viabroadcast/multicast.

(S5-2/S7) MBMS Service via Broadcast/Multicast Deactivation (UE CentricApproach)

When the periodic recount/comparison (S5-2) indicates that the number ofinterested mobile communication devices 3 has fallen below the broadcastthreshold t_(BM), the MCE 7 initiates deactivation of the MBMS servicevia broadcast/multicast. The delivery of the MBMS service viabroadcast/multicast is deactivated using conventional procedures (e.g.the procedures defined in the current version of the relevant 3GPPstandard) which a skilled person would readily understand.

After delivery of the MBMS service via broadcast/multicast has beendeactivated, the RRC layers of the mobile communication device 3 detectthe absence of the MBMS Service ID on the MBMS control channel andinitiate (re)activation of unicast delivery as described above for theMBMS service via unicast activation phase (S4) according to the UEcentric approach.

Summary—UE Centric Approach

In summary, therefore, in the UE centric approach, if the radio layersof the mobile communication device 3 detect that either: the countingprocedure is over and delivery of the service via broadcast/multicasthas not started; or a service that was previously delivered viabroadcast/multicast is no longer delivered via broadcast/multicast; thenan indication is provided from the radio layers to the applicationlayers to indicate that the mobile communication device 3 should makeuse of legacy mechanisms to receive the service via unicast. Theapplication layer in the mobile communication device 3 that receives theMBMS service via unicast can indicate receipt to the radio layers of themobile communication device 3 so that the mobile communication device 3can be counted for the MBMS services of interest. Then, when broadcastis available, the radio layers of the mobile communication device 3indicate accordingly to the application layer, which can then deactivatedelivery of the MBMS service via unicast using a NAS EPS bearer contextdeactivation procedure requested by the UE.

The UE centric approach provides benefits in terms of reduced impact ofthe implementation on the network, and provides improved backwardscompatibility with legacy systems.

Other Modifications and Alternatives

A number of detailed embodiments and variations have been describedabove. As those skilled in the art will appreciate, a number ofmodifications and alternatives can be made to the above embodiments andvariations whilst still benefiting from the inventions embodied therein.

It will be appreciated that although many of the logical/functionalentities of the communication system architectures 1-1 and 1-2 aredescribed as physically separate entities, two or more of the entitiesmay be combined into a single entity. For example, if the MCE 7 iscontrolling one base station, the MCE 7 may be provided as part of thebase station 5 in which case the M2 interface will be an internallogical interface within the base station 5. However, generally, as theMCE 7 controls more than one base station, the M2 Interface will stillbe visible (to the other base stations). Similarly, some or all of thefunctionality of a single entity may be provided as physically separateentities. For example, the SGW and PDN-GWs need not be combined and maybe provided separately.

It will be appreciated that although FIG. 20 shows a NULL Non AccessStratum (NAS) message being incorporated into the RRC Connection SetupComplete message the NAS message need not be a NULL message but may bemodified to any suitable value because the presence of the MBMS serviceslist is sufficient to indicate that the initiation of the activeconnection is for the purposes of counting.

It will be appreciated that although in the above embodiments theinformation identifying the number of interested mobile communicationdevices is advantageously provided as a list of information identifyingeach interested device. The information may be provided as a value (e.g.a cumulative total) representing the number of interested mobilecommunication devices counted in the counting procedure.

In the above embodiments, a mobile telephone based telecommunicationssystem was described. As those skilled in the art will appreciate, thesignalling techniques described in the present application can beemployed in other communications system. Other communications nodes ordevices may include user devices such as, for example, personal digitalassistants, laptop computers, web browsers, etc.

It will be appreciated that whilst, in the above embodiments informationis provided in the MBMS Session Start Request for letting the MCE 7 knowthat counting of interested mobile communication devices 3 is requiredbefore deciding to deliver an MBMS service using broadcast/multicasttransmission, the information could be provided by other means. Forexample, the information could be provided in advance, by the networkoperator, using OAM (Operation, Administration and Maintenance)signalling to pre-configure the MCE 7 to perform counting for all orspecific MBMS services. Moreover, it will be appreciated that theindication, to the mobile communication devices 3, that counting for aparticular MBMS service is required may be provided to each mobilecommunication device 3 via dedicated Radio Resource Control (RRC)signalling from the base station 5 that serves it.

In the embodiments described above, the various entities illustrated inFIGS. 3 to 9 are described as having each including transceivercircuitry. Typically, this circuitry will be formed by dedicatedhardware circuits. However, in some embodiments, part of the transceivercircuitry may be implemented as software run by the correspondingcontroller.

In the above embodiments, a number of software modules were described.As those skilled in the art will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to any ofthe various entities illustrated in FIGS. 3 to 9, as a signal over acomputer network, or on a recording medium. Further, the functionalityperformed by part or all of this software may be performed using one ormore dedicated hardware circuits. However, the use of software modulesis preferred as it facilitates the updating of the various entities inorder to update their functionalities.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

This application is based upon and claims the benefit of priority fromUnited Kingdom patent application No. 1018855.5, filed on Nov. 8, 2010,the disclosure of which is incorporated herein in its entirety byreference

The invention claimed is:
 1. A mobile communication device which isoperable to support a Multimedia Broadcast Multicast Service (MBMS), themobile communication device comprising: a transceiver circuit; and acontroller, comprising one or more processors configured to: receive,from a base station of a network providing the MBMS, via the transceivercircuit, a system information broadcast comprising MBMS information;determine, based on said system information broadcast, at least one MBMSservice of interest to be made available within a coverage area; andtransmit, via the transceiver circuit at radio resource control (RRC)connection establishment with the network, an RRC message other than anRRC connection request message having a cause value field, the RRCmessage including at least one identifier which indicates if the mobilecommunication device is interested in receiving the MBMS service.
 2. Amethod performed by a mobile communication device which is operable tosupport a Multimedia Broadcast Multicast Service (MBMS), the methodcomprising: receiving, from a base station of a network providing theMBMS, a system information broadcast comprising MBMS information;determining, based on said system information broadcast, at least oneMBMS service of interest to be made available within a coverage area;and transmitting, at radio resource control (RRC) connectionestablishment with the network, an RRC message other than an RRCconnection request message having a cause value field, the RRC messageincluding at least one identifier which indicates if the mobilecommunication device is interested in receiving the MBMS service.
 3. Abase station which is operable to support a Multimedia BroadcastMulticast Service (MBMS) in a network, the base station comprising: atransceiver circuit; and a controller, comprising one or moreprocessors, configured to: determine an identification of the MBMS;transmit, to a mobile communication device via the transceiver circuit,a system information broadcast comprising MBMS information fordetermining, by the mobile communication device, at least one MBMSservice of interest to be made available within a coverage area; andreceive, from the mobile communication device at radio resource control(RRC) connection establishment with the network, an RRC message otherthan an RRC connection request message having a cause value field, theRRC message including at least one identifier which indicates if themobile communication device is interested in receiving the MBMS service.4. A method performed by a base station which is operable to support aMultimedia Broadcast Multicast Service (MBMS) in a network, the methodcomprising: determining an identification of the MBMS; transmitting, toa mobile communication device, a system information broadcast comprisingMBMS information for determining, by the mobile communication device, atleast one MBMS service of interest to be made available within acoverage area; and receiving, from the mobile communication device atradio resource control (RRC) connection establishment with the network,an RRC message other than an RRC connection request message having acause value field, the RRC message including at least one identifierwhich indicates if the mobile communication device is interested inreceiving the MBMS service.
 5. The mobile communication device accordingto claim 1, wherein the controller is further configured to: register,via the transceiver circuit, the mobile communication device with thebase station; and initiate, when the mobile communication device is inidle mode, communication with the base station to establish the RRCconnection with the network.
 6. The mobile communication deviceaccording to claim 1, wherein the RRC message further includesinformation indicating that the RRC connection is established and thatthe mobile communication device is interested in receiving the MBMSservice.
 7. The mobile communication device according to claim 6,wherein the RRC message comprises a non access stratum (NAS) message. 8.The mobile communication device according to claim 7, wherein the NASmessage has a length set to zero.
 9. The mobile communication deviceaccording to claim 1, wherein the at least one identifier identifies oneor more MBMS services the mobile communication device is interested inreceiving.
 10. The mobile communication device according to claim 1,wherein the transceiver circuit is further configured to receiveinformation from the base station indicating release of the RRCconnection.
 11. The method performed by a mobile communication deviceaccording to claim 2, further comprising: registering the mobilecommunication device with the base station; and initiating, when themobile communication device is in idle mode, communication with the basestation to establish the RRC connection with the network.
 12. The methodperformed by a mobile communication device according to claim 2, whereinthe RRC message further indicates that the RRC connection is establishedand that the mobile communication device is interested in receiving theMBMS service.
 13. The method performed by a mobile communication deviceaccording to claim 12, wherein the RRC message comprises a non accessstratum (NAS) message.
 14. The method performed by a mobilecommunication device according to claim 13, wherein the NAS message hasa length set to zero.
 15. The method performed by a mobile communicationdevice according to claim 2, further comprising: receiving informationfrom the base station indicating release of the RRC connection.
 16. Thebase station according to claim 3, wherein the controller is furtherconfigured to: register, via the transceiver circuit, the mobilecommunication device with the base station; and enter, when the mobilecommunication device is in idle mode, communication with the mobilecommunication device to establish the RRC connection with the network.17. The base station according to claim 3, wherein the RRC messagefurther includes information indicating that the RRC connection isestablished and that the mobile communication device is interested inreceiving the MBMS service.
 18. The base station according to claim 17,wherein the RRC message comprises a non access stratum (NAS) message.19. The base station according to claim 18, wherein the NAS message hasa length set to zero.
 20. The base station device according to claim 3,wherein the controller is configured to: transmit information to themobile communication device indicating release of the RRC connection.